Injector pump for breech cooling of guns



Dec. 18, 1956 G. A. HAwKlNs INJECTOR PUMP FOR BREECH COOLING oF GUNS'Filed sept. 19. 1945 a- U ii 9,

United States Patent INJEcroR PUMP non BREECH coLiNC F GUNS eorge A.Hawkins, West Lafayette, Ind., assigner to Purdue University, Lafayette,Ind.

Application September 19, 1945, Serial No. 617,374 Y 2 Claims. (Cl.89-1) The inven-tion relates to means for cooling machine guns bylinjection of water or other liquids or fluid, and seeks to present apracticable pump device operable by lprior gun mechanism for supplying aliquid under pressure to a jet or other device at the gun chamber orbore.

lt is ajparticular purpose to present such a device adapted to supplycharges of Water to the gun at the rapid intervals corresponding to thefrequency of fire of current models of machine guns; which will also beof light weight, and small size, and adapted to be incorporated as apart of the gun without interfering with conventional use of the weapon.

Because of the delicate balance of forces in current models of machineguns, and the fact that any addition to the work required to beperformed by the recoil operated mechanism is likely to result in thestoppage from causes that would not otherwise have such effect, it is anobject of the invention to present a device which will require a minimumof work by the gun mechanism for itS operation. In this particular it isa purpose to cause the pump to function as part of the recoil mechanism,so that it will act as a resilient buffer to absorb some excess ofmomentum in the present recoiling parts of the gu-n and to convert apart thereof to counter recoil energy.

A further attainment in View is the perfection of details in the pump bywhich a minimum impedance o f a piston by liquid to be moved will besulered, and a maximum of ener-gy in the piston applied to compressionof liquid at an injector jet, without requiring complicated devices. i

Additional objects, advantages and lfeatures of invention reside in theconstruction, arrangement and cornbination of parts involved in theembodiment ofthe invention, as will be apparent or understood from thefollowing description and accompanying drawings wherein:

Fig. l is a vertical longitudinal section of 4the rear end of a machinegun in which my invention is embodied,

Fig. 2 is a cross section on the line 2 2 of Fig. '1;

Fig. 3 is a cross section on the hne 3 3 of Fig. l;

Fig. 4 is a rear elevation of the bolt and striker plate;

Fig. 5 is a fragmentary longitudinal section of a modification of thepump.

Referring more particularly to the details in the draw-- between thegrips as heretofore.

The back plate 13 has the usual buffer disc sleeve 15 in which elasticbuffer `discs have heretofore been mounted supported rigidly at the rearor outer end of the sleeve, and bearing against a buffer plate set inthet f butV all the discs and thepbuer plate are axiallyrboredf.

Y 2,774,281 Patented Dec. 1s, 195s ,Q I ice s o 'as to receive freelyslidable therethrough a piston rod 18 extending through the head 19 of apump cylinder 2 0, the head being tenoiied and threaded to screw intothe rear' interiorly threaded end of the sleeve 15 and against 4thediscs as a figid support o'r seat therefor. The tenon 21 is bored at its:forward end to receive a packing and gland around the rod 1S, as at 22,the rod 18 being snugly slidable through a reduced bore in the head. Apiston 23 4is fixed on the rod, reciprocable in the cylinder 20.

In the present instance the cylinder 20 is shown as a bored piece closedat its rear end by a plug 24. Set in the cylinder and confined betweenthe plug 24 and piston there is a helical spring 25 serving to hold thepiston yieldingly at the forward limit of its movement. The tension ofthe spring may be adjustable, if desired, by means of the plug 24. Thepiston may also be made adjustable on the rod to vary the length of theforwardly extended part of the latter, as will be understood.

The length of the cylinder bore greatly exceeds the length of Vtherequired stroke of the piston, so as to accommodate a spring of adequatelength.

The forward end of the rod 18 is in, and llongitudinally alined with,the path of the bolt 26 of the gun; and Va striker plate 27 yis mountedon the rear end of the bolt, to engage the end of the rod 1S, avoidingliabilityof deforming the material of the bolt and also serving toprotect and retain the sear and sear side against loose movement onimpact of the bolt with the rod 18. Thi-s plate 27 is held iin place bya dovetail bar 28 formed and fixed permanently to the back of the plate27 and set slidably in a corresponding dovetail `groove formed acrossthe extremity of the bolt. The bar 28 is of a length equal to the widthof the bolt, and with lthe latter fits slidably between the side platesof the receiver. In consequence, no fastenings are required for theplate 27, and it may be vtaken off manually when the bolt is taken .outof the receiver by manually pressing the plate 27 toward either sideuntil the bar 2S clears the groove across the end of the bolt.

The cylinder v20 of Figs. 2 and 3 is formed with an inlet port 30, ormore, adjacent -the forward end of the piston when in initial position,and two or more ports 31 immediately to vthe rear of the piston when insaid position. The cylinder has fitted and welded therearoundV amanifold ring 32, U-shaped in cross section, into which a supply pipe 33is set, and a U-bend pipe 34 `also has one end set in the manifold andits other end set in the port 30, forming a by-pass between the cylinderspaces at .opposite ends of the piston during a limited part of itsmovement. In a modification of the pump in Fig. 5, four ports 30' andfour ports 31 (three of each being shown) are formed in the cylinder,the two series in Ithe same relation ,to each other and to the piston asare the ports 30 and 31, and an interiorly channelled manifold ring 35is provided on the cylinder, broad enough to extend over and form commoncommunication between all of the ports 30 and 31'. The supply pipe 33isengaged in this manifold, but need for pipe 34 is eliminated, at thesame time that a Ireduction of impedance of piston and bolt movements isattained, which will be understood.

At a distance -rearwardly of the ports 31 an outlet 36 is formed throughthe wall of the cylinder, from which a high pressure pipe 37 is extendedforwardly alongside or under the receiver 11 and to the chamber of thegun, or to other location, so that liquid carried through the pipe maybe discharged into the gun chamber, or bore; the last named details notbeing shown since they comprise no part of the invention claimed herein.It may be stated, however, that it has heretofore been proposed toinject water into the breech of a gun as a cooling expedient, and theuse of :a jet requiring the water to be forced therethrough with aspraying eiect has been contemplated. Y

It may be seen that some extent of movement of the piston 23 from itsinitial position, shown in Fig. l, may occur before it passes beyond theports 31. Maximum high pressure is not developed in the outlet r'port 36until the piston does pass beyond these ports, which may be termedcut-off. In order to utilize this function to produce a very certainmeasurement and .instant high pressuredischarge vof liquid :at whatevernozzle there may be provided at the gun breech, I have` located in thepipe 37 a pressure regulating check valve 38, of suitable constructionto permit passage of liquid to the gun after the piston 23ypasses beyondthe ports 31.

vThe valve 38 may be constructed so as to'positively prevent return ilowofthe liquid toward the pump, and also may ,be` :adjustablejor providedwith a spring of strength suicient to prevent ow toward the gun cham-.ber until the pressure at the port v36 is higher than the hydrostatichead Ade veloped by inertia. of the water be- Y fore the piston in theearly movement of the latter towardor to the rear sides of theports 31.

'Ihepump is so proportioned in relation to the movement of the r`d7718by the bolt, that it may be adjusted to supply. inthe neighborhood ofVthree or more grams of water to the `gun on each operation of thepiston in the caseof a .50 caliber machine gun of the type'indicated,and this'su'pply may be varied by substitutingpistons' and cylinders ofdifferent diameters, or by adjusting the piston on the rod18 by means ofnuts 39 screwed on the rod before and behind the piston. The piston bodybetween the nuts may be of conventional construction,

suitable. to the use disclosed. The cylinder is shown with a forwardshoulder which serves as a stop for the piston and.. thereforeadjustment of the piston longitu'dinally Von the rodV 18 withcorresponding changes of position of the nuts, determines Athe extent towhich the rod projects into the receiver 171 and the length of stroke of'the piston. Parts of the supply pipe 33 and high pressure pipe '37 maybe flexible conduit to facilitate remov-al and replacement of the backplate, and for other purposes. l v

I'na gun 'of' the kind indicated, the bolt by which my rod: 18 isoperated has a weight in the neighborhood of five, pounds and -moves byrecoil over a total distance of seven ahdfone-eighth inches, andassuming the diameter ofthe pump bore to `be l5 mm. the device isconstructed `inthe present illustrated instance to utilize approximatelylby'theboltfrnay have some impeding effect lon the bolt,

which may, be compensated for by adjustment ofthe oil buer devicecustomarily present in the barrel recoil' device in the Vgun indicated,or other recoil device, and. ad-

justment vof `the plug 214lto cause rn'o'refeife'ctive recoil 4function'ofuthecspring Y25. These adjustments maintain orihcreasethe rate of`reofthe gun.

As the lrod" 18 is pushed rearwardly by the bolt, the piston rstdisplaceswater from the rearpart of the cylinderfthrfough fhefports 31,and forwardly through the pipe 34, intofthe Aextreme forwardpart ofthecylinder, and against Athe forward side-of the piston 23'. At the sametime the spring 25 Vis progressively compressed, with increasing`absorption; ofjinertiaof the-bolt. A-S

. recoil movement. While I have disclosed my invention in the best formthe piston passes rearwardly of the ports 31, cut-off there preventsfurther -displacement of water through the ports 31, and a highresistance ,to further movement of the piston develops by the inertia ofliquid in advance of the piston toward the rear in the cylinder andstanding in the pipe 37 to the gun chamber. The momentum of the bolt isassisted in this work by the momentum of the liquid in motion throughthe bypass pipe 34 to the forward side of the piston, and aiding, as aliquid piston, in the rearward movement of the piston 23. When cutoioccurs at the ports 31, inow of water from the 'slipply 33 to themanifold ring will avoid dissipation of the liquid piston energy beforeit has been materially utilized against the piston 23.

The spring 25 is' preferably one capable of counteracting the inertia ofthe bolt, less that dissipated in operation of the piston upon theliquid, although the discs 16 may be permitted to perform some part ofthis function, the plate 27 engaging the buffer plate 17 'in the samemanner as the bolt itself, has heretofore done.

It is my practice, in one manner of u'tlizationoffthe invention, tomaintain the water supply at 33 under pres-V sure, so as to minimize tothat extent impedance of thel piston after cut off 'at the ports 31, thepressure supply Y being formally indicated as a storage reservoir 40from which the pipe `33 leads, an air chamber 41 being indicated; also apump 42 having .an outlet 43 delivering to the'reservoir, andasupplyduct 44 connected to its. intake. The pump is adapted to be otherwisemounted and connected to a recoiling member, and this is con templated.v

Ill this type of gun a separate recoil action is provided for thebarrel.. operatively connected with the cartridge,l

v there. is an initialgreco'il interaction 'and coupling betweenthewbarrel unit and the bolt unit, including an accelerator device onthe barrel: unit by which impetus may be added tothe movement of thebolt, and the recoil of 'the barrel unit is adjustable so that thisincrement of motion `in the boltmay be increased, to compensate for theenergyrequired in operating the valve. There is acoupling ofrbol't andbarrel also during a small part of their'nal counterin Vwhich I haveconstructed and used the same, it Will nevertheless be` understood thatthis is exemplary only,

and that improvement in design and proportions 'com` Arnen'surate with.requirement of use, strength of material,

. mentwith the claims hereunto appended.

I claim: p

1,v In, an injector pumpfor cooling a gun having a receiver body, abarrel, a reciprocating bolt and' a bolt buffer assembly,` comprising,Va pump cylinder,- closed-at vits`I rearward; end: and provided withl areduced, axially bored,threaded forward head portion, said cylinderadapted to. be threadablyfsecurediin coaxial. relationv to the rearwardend of said bolt Vbuffer assembly, a' piston jrocl connected at itsforward end to said reciprocating Vbolt and extending axially'V andrearwardlythrough said boltbulfer'assembly, said" axial bore inheadportionon said-pump cylinder 'and into the Vforward portionof 'saidYiipump cylinder, a piston secured on the rearward'zendofsaid-:piston rodand Vslidabley in said'Y pump cylinde'xg-a spring insaid pump cylindernormally biasing said pistonV Vinfarforw'ard direction, an annularchannel? surrounding Y psaicljpurnpj; cylinder,V a1 rstl pipe connectingsaid iannularj channel with a source of liquid coolant, a series ofradial ports in said cylinder wall communicating between vsaid annularchannel and said pump cylinder, a second pipe communicating between saidannular channel and the forward portion of said pump cylinderimmediately forward of said piston when said piston is at its fullforward position in said pump cylinder, a third pipe communicatingbetween said pump cylinder at a point substantially rearward of saidpiston, when said piston is in said full forward position, and a barrelon said gun, said piston acting upon recoil to move in a rearwarddirection to force said liquid coolant into said barrel of said gun anda pressure regulating valve on said third pipe.

2. In an injector pump for cooling a gun having a receiver body, abarrel, a reciprocating bolt and a bolt buer assembly, comprising a pumpcylinder axially secured at its forward end to said buter assembly, avspringbiased piston slidably mounted within said cylinder and connectedto said reciprocating bolt of sa'id gun, an inlet and an outlet portformed on said cylinder, said inlet port in communication with eachother, a manifold mountedV on said cylinder connecting said inlet portW-ith said second port, and said piston being initially located betweensaid irst and second ports.

l References Cited in the le of this patent UNITED STATES PATENTS543,567 Browning July 30, 1895 1,073,452 White Sept. 16, 1913 1,216,460Kilgore Feb. 20, 1917 1,401,667 Brown Dec. 27, 1921 2,376,321 AlbertsonMay 22, 1945

